1. Field of the Invention
The present invention relates to a photosemiconductor encapsulating resin composition, a photosemiconductor encapsulating hardened substance obtained by hardening the composition, and a photodiode encapsulated with the hardened substance.
2. Description of Prior Art
Already known as the photosemiconductor encapsulating resin composition used is, for example, a transparent resin composition composed of an alicyclilc type epoxy resin and an acid anhydride hardener (JP-A No. 6-316626), and this publication specifically discloses a photosemiconductor encapsulating resin composition, further containing a methacrylic acid-based phosphate for improving close adherence with a photosemiconductor.
Recently, a light emitting diode emitting light of short wavelength such as blue light, ultraviolet light and the like, and a white color light emitting diode obtained by combining these light emitting diodes with a fluorescent body are practically utilized. To encapsulate these light emitting diodes, encapsulating resin composition are required that transmittance for blue light to ultraviolet light is high and transmittance does not decrease by heat generation in operation (hereinafter, referred to as heat-resistance) or does not decrease by light of short wavelength from a light emitting diode chip, namely, even if irradiated with light of short wavelength having high energy such as blue light, ultraviolet light and the like for a long time, coloration does not occur(hereinafter, referred to as ultraviolet-resistance).
As the resin composition for encapsulating a light emitting diode, a resin composition containing a non-aromatic type epoxy resin as an effective ingredient has been suggested, specifically, a light emitting diode resin composition containing
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate and methylhexahydrophthalic anhydride as an effective ingredient has been disclosed (JP-A No. 2000-196151).
The present inventors have investigated a transparent resin composition composed of an alicyclic type epoxy resin and an alicyclic carboxylic anhydride, for example, a hardened substance of an epoxy resin composition containing    3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate and methylhexahydrophthalic anhydride as an effective ingredient, used as a resin composition to seal a light emitting diode, and a problem has been made clear that a hardened substance of this composition is, directly after hardening, already colored though transparent, and when stored at high temperature (150° C.), the composition is further colored.
An object of the present invention is to provide a photosemiconductor encapsulating resin composition giving a hardened substance excellent in light transmittance from immediately after hardening, excellent in light transmittance even if irradiated with blue light or ultraviolet light for a long time or used at high temperature for a long time, namely, excellent in any of initial transmittance, ultraviolet-resistance and heat-resistance.